Rotary impact rock breaking equipment

ABSTRACT

Rock breaking equipment wherein a power driven rotor has hammers pivotally secured thereto with each hammer carrying a striking tip. The hammers are designed as compound pendulums with the striking tip on the major axis of symmetry for the pendulum. The hammers are also made to ensure that they are also capable of a combination of radial and rotational movement relative to the axis of rotation of the rotor. As a result of the unique construction of the hammers and rotor, the operational impact loading applied to the hammer pivot is only a minor proportion of that applied to the hammer striking tip.

D United States Patent [151 3,695,724 Taylor [451 Oct. 3, 1972 [54]ROTARY IMPACT ROCK BREAKING 2,537,702 1/1951 Putnam ..l73/99 X EQUIPMENT2,691,511 10/1954 Lundquist ..173/99 X Fm 2512.23 $412.22 3433;; burg,Transvaal Province, Republic of South Afnqar- Primary Examiner-Emest R.Purser 73 Assignee; g ud g d 1 Attomey-Shoemaker and Mattare vestmentCompany Limited, Johannesburg, Republic of South Africa [57] ABSTRACT 22Filed; Sept, 1970 Rock breaking equipment wherein a power driven rotorhas hammers pivotally secured thereto with each [2]] Appl- N05 70,309hammer carrying a striking tip. The hammers are designed as compoundpendulums with the striking tip Related Applicahon Dat. on the majoraxis of symmetry for the pendulum. The [63] Continuation-impart of Ser.No. 774,061, Nov. mm r are also m de o ensure tha hey are also 7, 1968,abandon d, capable of a combination of radial and rotational movementrelative to the axis of rotation of the rotor. 52 US. Cl. ..299/69,173/99, 299/85, AS a result of the unique construction of the hammers299/94 and rotor, the operational impact loading applied to [51] Int. Cl..E21c 25/02 hammer pivot is only a minor proportion of that 58 Field ofSearch ..299/37, 62, 69, 7o, 81, 85, 31 3 9 9??? ?{}FP ffF kR P [56]References Cited .1f .f.f P g res UNITED STATES PATENTS 1,195,396 8/1916 Recen.... ..299/

1 ROTARY IMPACT ROCK BREAKING EQUIPMENT BACKGROUND OF THE INVENTION Thisapplication is a continuation-in-part of application Ser. No. 774,061filed Nov. 7, 1968, now abandoned, and relates to rock breakingequipment and more particularly to equipment which may be used formining or tunnelling operations.

Where hard rock is to be mined or tunnelled into there is no efficientmachine to effect this operation. The tunnelling machines availablerequire high pressures against the rock face and excessive wear anddamage to these machines occur with hard rock conditions. Even with rockwhich is of a softer nature, these machines are expensive because oftheir weight and auxilliary equipment necessary to provide the pressuresagainst the rock faces.

OBJECTS OF THE INVENTION It is an object of the present invention toprovide rock breaking equipment which will be less expensive tomanufacture than that presently available, and which will be useful foroperations in both hard and soft rock, when incorporated in a rockbreaking machine.

It is a further object of this invention to provide a rock breakerwherein a series of swinging hammers is provided on a rotor with eachhammer carrying a suitable rock breaking tip.

Another object of this invention is to provide for the hammers to bedesigned as compound pendulums each with the striking tip substantiallyon the line of major symmetry of the hammer.

A still further object is to provide a rock-breaking hammer whereinsubstantially no shock load is transmitted to the hammer pivot.

SUMMARY OF THE INVENTION According to this invention there is providedrock breaking equipment including a rotor carrying at least one hammerpivotally secured thereto with the pivot axis eccentric to butsubstantially parallel to the axis of rotation of the rotor and with thecenter of gravity of the hammer eccentric to the pivot and in a mannerallowing a combination of both radial and rotational movement of thehammer striking tip relative to the axis of rotation of the rotor undernormal operating conditions for the equipment.

Analysis of the action of a rotor carrying a series of hammers pivotallysecured thereto shows that if the inter-relationship of the eccentricityof the pivots and the center of gravity of the hammers and the center ofrotation of the rotor is not calculated and not made to meet certainrequirements the result is excessive wear of parts or ineffectualoperation or a construction which operates in the manner of a hammermill where The invention also provides for the rotor to carry a pair ofstops for each hammer to limit the swinging movement thereof ifrequired.

Yet another feature of this invention provides for the hammer strikingtip to be carried on the outer periphery of a web or webs of resilientmaterial including means for limiting the radial extension of the webunder the centrifugal force occurring during operation of the equipment.

The preferred design of the rotor and swing hammers is such that whenthe hammer strikes the rock surface to be broken, no shock load isthrown back onto the hammer pivot. It is also desirable that all theenergy given up by the hammer in striking the rock is restored to thehammer by the centrifugal force applied thereto during the remainingportion of the revolution of the rotor in order to bring the hammer backinto the striking position at the appropriate time.

This is difiicult to achieve in practice with a free swinging compoundpendulum hammer mounted eccentrically to the axis of rotation of therotor although the first preferred design feature is fairly simplyarranged.

Practical considerations may make it desirable to have resilient stopspositioned to prevent over swinging of each hammer in either directionabout its pivot.

If the hammer construction includes the feature mentioned aboveinvolving a web or webs of resilient material, it will be realized thatthese webs help substantially in restoring the speed of the hammer tip.

In essence, the hammer acts as a compound pendulum to obtain a balancecontrolling the operational impact loading applied to the hammer pivotto a minor proportion of that applied to the hammer striking tip. Theeccentricity of the center of gravity of the hammer relative to itspivot, the spacing of the striking tip from the hammer pivot, and thepolar radius of gyration of the hammer all cooperate to result in verylittle shock load being transmitted to the hammer pivot.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the inventionare illustrated in the accompanying diagrammatic drawings in which:

FIGS. 1 and 2 illustrate a solid hammer arrangement on a rotor.

FIG. 3 shows a more detailed view of one hammer and stop block of thetype shown in FIGS. 1 and 2.

FIG. 4 shows a preferred shape of cutting tool, and

FIGS. 5 and 6 illustrate hammers having resilient web portions.

DETAILED DESCRIPTION OF THE INVENTION Referring firstly to FIGS. 1 and2, wherein like reference numerals refer to like parts throughout theseveral views, a rotor comprising a plurality of spaced side plates 2 ismounted on a rotatable axle l for rotation therewith. A plurality ofhammers 4 are mounted between the spaced side plates 2 about a hammerpivot pin 3 carried by the plates for pivotal movement of the hammers 4relative to the rotor. A suitably sealed and lubricated bush or bearing5 is disposed about the hammer pivot pin 3. A tungsten carbide tippedtool 7 is inserted into the hammer for striking rock to be broken. Thehammer is shown in FIG. 1 in solid lines in position ready for strikingrock, and in dashed lines at 6 in position after striking the rock andagainst a back resilient stop G. A front resilient stop F is disposed onthe rotor in a position to limit forward movement of the hammers 4.Still referring to FIG. 1, the hammer has a pivotal axis B spaced fromthe axis of rotation A of the rotor. The distance from C to B is equalto the radius of gyration of the hammers about their pivot B. The centerof gravity of the hammer when it is about to strike the rock isindicated at D, and after the hammer has struck the rock and just beforestriking the back stop G, the hammers center of gravity is at D,. Thepoint relative to the rotor at which the insert strikes the rock isindicated at E.

From the above construction, it will be appreciated that a second pivotpin would usually be placed symmetrically to the pin 3 on the oppositeside of the rotor axle 1. With such an arrangement, two hammers operateon a single path but, depending on the overall design, one, three, fouror more hammers could be used per path.

Furthermore, sufficient paths would be incorporated on the rotor (onlythree are shown in FIG. 2) to cut a swathe of the desired width.

Ideally the dimensions should accord with the following formula:

also as far as possible B F should equal B E and B G should equal B E,but this is not so necessary as these stops are resilient and would notgive sharp shock loads to the hammer.

Furthermore, the energy lost by the hammer when hitting the rock shouldequal the energy required to move the hammer towards A against thecentrifugal force, until its center of gravity reaches position D,. Thismovement towards A is measured by A D minus A D This latter requirementmay be more difficult to accomplish bearing in mind the wear on theinserts which tends to be high at high tip striking speeds. The stop Gis, therefore, used to prevent excessive back swing.

The hammer, after swinging back (and possibly hitting G), will swingforward and will tend to swing past the desired striking point E unlessprevented from so doing by the stop F.

Referring now to FIGS. 3 and 4 which give a practical example of thehammer and stop construction for use in a rock breaking machine, a stopblock 21 and hammer 22 are each mounted between backing discs one ofwhich is indicated at 23 and it will be understood that only one stopblock and hammer is shown in FIG. 3. A plurality of such assemblies willpreferably be pro vided for each width of cutting tool as well as aseries of similar arrangements along the length of the rotor to give therequired width of cut.

The block 21 is mounted between the discs 23 by means of pin 24 andcirclips will be preferred for this purpose. The block 21 is heldagainst the rotor shaft 25 along an arcuate section 26 and fluidpassages 27 are provided through the shaft and stop block 21 toterminate inside the stops 28 themselves which are made as cylindrical,metal reinforced, hollow rubber bulbs similar to the commerciallyavailable Oscillith bush construction. The passages 27 also open throughapertures 29 so that fluid forced through the passages can also beejected onto the rock face being cut. In minning operations, forexample, this fluid will preferably be water.

The stops 28 absorb the energy of the hammers 22 as they are brought torest against them and the resilience in the construction returns thisenergy, less the inherent losses to the system.

The hammer 22 is mounted to swing freely on pin 30 and is constructedaccording to the principles described above. Resilient blocks 31 areprovided on the hammers also and positioned to strike against stops 28on stop blocks 21 on each side of the hammer as indicated in thedrawings.

The outer end of the hammer has a socket 32 to receive the cutting tool33 and this socket has a tapered surface to correspond to the tool whichis illustrated in FIG. 4. The socket is also radiused at 34 to providespace for the shoulder 35 on the tool 33.

The tool is shaped to prevent excessive stresses occurring on the toolduring use and the tapered shank 36 terminates at the narrow end in aparallel screw threaded portion 37 which has a suitable nut associatedtherewith to enable the tool to be secured in the socket 32 of thehammer 22.

The wider end of the shank terminates in the rounded shoulder 35 of thehead portion 38 which head is slotted at 39 to carry the tunsten carbidestriking tip 40. This insert is secured in accordance with usualpractice but it will be appreciated from FIG. 4 that the striking tip issymmetrically curved along the width of the head 38 and bounded by sides41 and 42 which are approximately at right angles to each other. Side 41is made to be at a very much larger angle to the axis of the tool thanis side 42.

It has been found that the construction indicated above results in aneffective operation of rock breaking without involving heavy machinery.

Referring now to FIGS. 5 and 6 of the drawings, a hammer 16 is shownmounted on two resilient webs 15. The resilient webs 15 are made in theform of annular discs with the thickness inversely proportional to theradius at that point, and the hammer 16 is in the form of a ring heavilyweighted in the zone contained by a circle of diameter QT and highlyconstructed elsewhere. The webs 15 are clamped between a drive boss 13and a pair of clamps 14. The drive boss 13 is attached to a drive shaft11 for the rotor, the drive boss being eccentrically mounted in such amanner that when the hammer swings back relative to the boss, the centerof gravity of the rotating portion of the hammer approaches a point Pwhich corresponds to the axis of rotation of the drive shaft of therotor. A water channel 12 is formed down the center of the drive shaft11. A pair of clamping rings 17 are disposed in clamping relationship onthe outer edge of the webs for holding the webs to hammer 16. A waterchannel 18 is formed in the hammer 16 for conveying water in front ofthe striking point of the hammer. The water also acts as a coolant forthe webs 15. A plastic-impregnated wire rope restrainer 19 or the likeis disposed over the drive boss 13 to prevent undue distortion of thewebs 15 when subjected to the centrifugal forces of the hammer. When thehammer is stationary, this restrainer is not in contact with the boss13. A tungsten carbide tipped tool 20 is inserted into the hammer forstriking rock to be broken. A water channel (not shown) is also formedin the drive boss 13 to enable water from channel 12 to flow in thespace between webs 15. The pivot center of the device is indicated at Qand this center may vary slightly relative to the body of the hammer dueto the resilient web distorting under the centrifugal force of thehammer, which as mentioned previously is limited by the restrainer 19.The center of gravity of the rotating portion of the hammer in strikingposition is indicated at S, and the center of gravity of the rotatingportion of the hammer in a position after striking rock is indicated at8,. The point relative to the rotation at which the hammer insertstrikes rock is indicated at T. The distance from R to Q is equal to theradius of gyration of the rotating portion of the hammer about Q.

Ideally the dimensions should accord with the followin g formula:

Furthermore, the energy given up by the hammer in hitting the rockshould be equal to that required;

a. to move the center of gravity of the hammer closer to the axis Pagainst the centrifugal force of the hammer by the amount P S minus P8,,

plus

b. the energy required to distort the resilient webs by twisting themsubstantially about their axis.

It should be noted that due to the elastic properties of the webs itwill be found that there is an optimum rotational speed at which thehammer on its swing back will be in the striking position just at thecorrect time to strike the rock.

The optimum speed will not vary very much with variations in the energyexpended per blow, for any given hammer-web combination. There is,however, an upper limit to the energy expended per blow which is thekinetic energy of the hammer rotating at the speed at moment of impact.

The speed of rotation of the hammer at moment of impact will normally befaster than the normal rotor speed due to its added pendulum like swingrelative to the rotor.

From the above, it will be appreciated that the hammer and rotor designcan also be adapted for more efficient operation of hammer mills than ispossible with those mills of presently available constructions. Further,where the equipment is adapted for mining or tunnelling operations awide variety of designs can be made to give useful results. For example,the rotor can be made to revolve about a second axis at an angle to theprimary axis of rotation in order that a circular tunnel or shaft can bebored into the rock. This will necessitate variations in hammerarrangements along the length of the rotor to give approximatelyequivalent traverse across the rock per cutting blow.

Variations in the shapes and sizes of tunnels, shafts and holesgenerally can be obtained using this type of equipment by the controlledmovement of the abovementioned second axis.

From the above it will be understood that the principle of rock breakingdoes not require the high pressures heretofore necessary for machinesfor the operations referred to, thus reducing the costs of the equipmentand increasing efficiency.

As this invention may be embodied in several forms without departingfrom the spirit or essential characteristics thereof, the presentembodiment is therefore illustrative and not restrictive, since thescope of the invention is defined by the appended claims rather than bythe description preceding them, and all changes that fall within themetes and bounds of the claims or that form their functional as well asconjointly cooperative equivalents, are therefore intended to beembraced by those claims.

I claim:

1. Rock breaking equipment comprising, a power driven rotor mountedabout an axis of rotation, at least one hammer freely pivotally mountedto said rotor and having a polar radius of gyration, the pivotal axis ofsaid hammer eccentric to and substantially parallel to the axis ofrotation of the rotor, the center of gravity of said hammer eccentric toits pivot by a predetermined distance, a striking tip carried by saidhammer spaced from the pivot of said hammer by a predetermined distance,the product of the two predetermined distances approximating the squareof the polar radius of gyration of the hammer, means mounting saidhammer to said rotor for both radial and rotational movement of thehammer and its striking tip relative to the axis of rotation of therotor, the striking tip of the hammer lying substantially on a lineextending through the pivot axis and center of gravity of the hammer sothat when the hammer strikes the rock surface to be broken substantiallyno shock load is transmitted to the hammer pivot due to theinterrelationship of the eccentricity of the center of gravity of thehammer relative to its pivot, the spacing of the striking tip from thehammer pivot, and the polar radius of gyration of the hammer, and stopmeans operatively associated with the hammer to limit pivotal movementthereof between predetermined limits.

2. Rock breaking equipment as in claim 1, wherein a plurality of hammersare freely pivotally mounted to said rotor.

3. Rock breaking equipment as in claim 1, wherein said hammer is carriedon the outer periphery of a flexible resilient web secured to saidrotor.

4. Rock breaking equipment as in claim 3 wherein means are provided forlimiting the radial extension of the web under centrifugal forceoccurring during operation of the equipment.

5. Rock breaking equipment as claimed in claim 1 in which the rotorcarries a pair of stops for each hammer to limit the swinging movementthereof.

6. Rock breaking equipment as claimed in claim 5 in which each hammercarries a resilient stop positioned to cooperate with the stops carriedby the rotor.

7. Rock breaking equipment as claimed in claim 5 in which each hammerand the stops therefor are mounted on pins between discs forming part ofthe rotor.

8. Rock breaking equipment as claimed in claim 5 in which the stops areresilient stops.

9. Rock breaking equipment as claimed in claim 8, in which the stops areformed as metal reinforced cylindrical hollow rubber bulbs.

10. Rock breaking equipment as claimed in claim 9 in which the rotor hasfluid passageways therein communicating with the stops and with outletapertures in the rotor.

11. Rock breaking equipment as claimed in claim 1 in which the strikingtip is carried by a tool removably held in the hammer.

12. Rock breaking equipment as claimed in claim 11 in which the tool hasa tapered shank fitted in a complementary socket in the hammer and thestriking tip is a tungsten carbide insert in the tool.

1. Rock breaking equipment comprising, a power driven rotor mounted about an axis of rotation, at least one hammer freely pivotally mounted to said rotor and having a polar radius of gyration, the pivotal axis of said hammer eccentric to and substantially parallel to the axis of rotation of the rotor, the center of gravity of said hammer eccentric to its pivot by a predetermined distance, a striking tip carried by said hammer spaced from the pivot of said hammer by a predetermined distance, the product of the two predetermined distances approximating the square of the polar radius of gyration of the hammer, means mounting said hammer to said rotor for both radial and rotational movement of the hammer and its striking tip relative to the axis of rotation of the rotor, the striking tip of the hammer lying substantially on a line extending through the pivot axis and center of gravity of the hammer so that when the hammer strikes the rock surface to be broken substantially no shock load is transmitted to the hammer pivot due to the interrelationship of the eccentricity of the center of gravity of the hammer relative to its pivot, the spacing of the striking tip from the hammer pivot, and the polar radius of gyration of the hammer, and stop means operatively associated with the hammer to limit pivotal movement thereof between predetermined limits.
 2. Rock breaking equipment as in claim 1, wherein a plurality of hammers are freely pivotally mounted to said rotor.
 3. Rock breaking equipment as in claim 1, wherein said hammer is carried on the outer periphery of a flexible resilient web secured to said rotor.
 4. Rock breaking equipment as in claim 3 wherein means are provided for limiting the radial extension of the web under centrifugal force occurring during operation of the equipment.
 5. Rock breaking equipment as claimed in claim 1 in which the rotor carries a pair of stops for each hammer to limit the swinging movement thereof.
 6. Rock breaking equipment as claimed in claim 5 in which each hammer carries a resilient stop positioned to cooperate with the stops carried by the rotor.
 7. Rock breaking equipment as claimed in claim 5 in which each hammer and the stops therefor are mounted on pins between discs fOrming part of the rotor.
 8. Rock breaking equipment as claimed in claim 5 in which the stops are resilient stops.
 9. Rock breaking equipment as claimed in claim 8, in which the stops are formed as metal reinforced cylindrical hollow rubber bulbs.
 10. Rock breaking equipment as claimed in claim 9 in which the rotor has fluid passageways therein communicating with the stops and with outlet apertures in the rotor.
 11. Rock breaking equipment as claimed in claim 1 in which the striking tip is carried by a tool removably held in the hammer.
 12. Rock breaking equipment as claimed in claim 11 in which the tool has a tapered shank fitted in a complementary socket in the hammer and the striking tip is a tungsten carbide insert in the tool. 